Black Box ACR1000A-T Manual De Usuario

ServSwitch Agility and Agility Dual

724-746-5500   |   blackbox.com 

Page 38

Appendix B. Troubleshooting

Problem: The video image of the ServSwitch Agility receiver shows horizontal lines across the screen. 

This issue is known as Blinding because the resulting video image looks as though you’re viewing it through a venetian blind. 

When video is transmitted by ServSwitch Agility units, the various lines of each screen are divided up and transmitted as separate 
data packets. If the reception of those packets is disturbed, then blinding is caused. The lines are displayed in place of the missing 
video data packets. 

There are several possible causes for the loss of data packets:

•  Incorrect switch configuration. The problem could be caused by multicast flooding, which causes unnecessary network traffic.

This is what IGMP snooping is designed to combat, however, there can be numerous causes of the flooding. 

•  Speed/memory bandwidth issues within one or more switches. The speed and capabilities of different switch models varies

greatly. If a switch cannot maintain pace with the quantity of data being sent through it, then it will inevitably start dropping 
packets.

•  One or more ServSwitch Agility units may be outputting Jumbo frames due to the video resolution (2048 horizontal pixels)

being used. If jumbo frames are output by a ServSwitch Agility unit, but the network switches have not been configured to use 
jumbo frames, the switches will attempt to break the large packets down into standard packets. This process introduces a cer-
tain latency and could be a cause for dropped packets.

•  One or more ServSwitch Agility units may be using an old firmware version. Firmware versions prior to v2.1 exhibited an issue

with the timing of IGMP join and leave commands that caused multicast flooding in certain configurations.

Remedies: 

•  Ensure that

 is enabled on all switches within the subnet.

•  Where each ServSwitch Agility unit is connected as the sole device on a port connection to a switch, enable

 to reduce unnecessary processing on each switch.    

•  Check the video resolution(s) being fed into the ServSwitch Agility transmitters. If resolutions using 2048 horizontal pixels are

unavoidable then ensure that 

 are enabled on all switches.

•  Check the

 on the switches. If Store and forward is being used, try selecting Cut-through as this mode 

causes reduced latency on lesser switch designs.  

•  Ensure that one device within the subnet is correctly configured as an

, usually a layer 3 switch or multicast rout-

er.

•  Ensure that the firmware in every ServSwitch Agility unit is version 2.1 or greater.

•  Try adjusting the transmitter settings on each ServSwitch Agility to make the output data stream as efficient as possible. See

 for details.

Problem: The audio output of the ServSwitch Agility receiver sounds like a scratched record.

This issue is called Audio crackle and is a symptom of the same problem that produces blinding (see previous page). The issue is 
related to missing data packets.

Remedies: 

As per blinding discussed above.